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A patient with a sore throat and fever had a throat smear stained with Gram's method, revealing Gram-positive cocci in chains. What is the most likely causative agent?
- A. Streptococcus pyogenes
- B. Staphylococcus aureus
- C. Neisseria gonorrhoeae
- D. Enterococcus faecalis
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pyogenes. This bacterium is known to cause sore throat and fever, commonly referred to as strep throat. Gram's stain showing Gram-positive cocci in chains is characteristic of Streptococcus species. Streptococcus pyogenes is a beta-hemolytic bacterium that forms chains and is a common cause of bacterial pharyngitis. Staphylococcus aureus (B) is a Gram-positive cocci that forms clusters, not chains. Neisseria gonorrhoeae (C) is a Gram-negative diplococcus and is not associated with sore throat. Enterococcus faecalis (D) is a Gram-positive cocci that can cause infections but is not typically associated with sore throat.
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From a medicinal herb a certain phytopathogenic microorganism was secured. In the nutrient medium it forms "fried egg"colonies. What is the most likely agent?
- A. Mycoplasma B.Yeasts C.Actinomycetes D.Nocardia E.Pseudomonas Legionella
Correct Answer: C
Rationale: Step 1: "Fried egg" colonies typically refer to colonies with a raised center and flattened periphery, resembling the appearance of a fried egg.
Step 2: Actinomycetes are filamentous bacteria known to form "fried egg" colonies in nutrient medium.
Step 3: Actinomycetes are commonly found in soil and are known to be phytopathogenic microorganisms.
Step 4: Actinomycetes produce secondary metabolites with medicinal properties, making them a likely agent from a medicinal herb.
Overall, the correct answer is C (Actinomycetes) as they fit the description provided in the question and are commonly associated with the given scenario. The other choices are incorrect as they do not exhibit the specific characteristics mentioned in the question or are not typically associated with forming "fried egg" colonies in nutrient medium.
Rotaviruses:
- A. The NSP4 nonstructural protein of rotaviruses acts in a toxic-like manner.
- B. Disease can be significant in infants and adults
- C. Cannot survive the acidic environment in the stomach
- D. Prevents the absorption of water, but do not cause a net secretion of water and loss of ions
Correct Answer: A
Rationale: The correct answer is A because the NSP4 nonstructural protein of rotaviruses indeed acts in a toxic-like manner by disrupting calcium homeostasis, leading to diarrhea. Choice B is incorrect as rotaviruses can cause significant disease in infants, but not typically in adults. Choice C is incorrect as rotaviruses are resistant to stomach acid. Choice D is incorrect as rotaviruses cause a net secretion of water and loss of ions, contributing to diarrhea.
All of the following viruses are enveloped EXCEPT:
- A. Hepatitis C virus
- B. Hepatitis B virus
- C. Hepatitis A virus
- D. Hepatitis D virus
Correct Answer: C
Rationale: The correct answer is C: Hepatitis A virus. This is because Hepatitis A virus is a non-enveloped virus, while choices A, B, and D are all enveloped viruses. Enveloped viruses have a lipid bilayer membrane surrounding their protein capsid, aiding in their ability to infect host cells. Hepatitis C, B, and D viruses all possess this lipid envelope, making them enveloped viruses. Hepatitis A virus, on the other hand, lacks this lipid envelope and is classified as a non-enveloped virus. Therefore, the correct answer is C.
Sterilization is a process that:
- A. Destroys most microorganism, but spores remain viable
- B. Leads to complete destruction of all microorganisms, including resistant forms such as spores
- C. Reduces the number of microorganisms on the surface of the skin
- D. None of the above
Correct Answer: B
Rationale: The correct answer is B because sterilization is the process of completely destroying all microorganisms, including resistant forms like spores, ensuring no viable organisms remain. This is crucial for ensuring complete elimination of potential pathogens. Choice A is incorrect because sterilization should eliminate all microorganisms, including spores. Choice C is incorrect as it describes disinfection, not sterilization. Choice D is incorrect because sterilization aims to eradicate all microorganisms, not leave any viable ones behind.
N. Meningitidis grows on
- A. Levine agar
- B. Lowenstein-Jensen agar
- C. TCBS agar
- D. Chocolate agar
Correct Answer: D
Rationale: The correct answer is D: Chocolate agar. Neisseria meningitidis is a fastidious organism that requires enriched media for growth. Chocolate agar contains heat-treated blood that provides essential nutrients for the growth of N. meningitidis. The other choices, A: Levine agar, B: Lowenstein-Jensen agar, and C: TCBS agar, do not provide the specific nutrients required for the growth of N. meningitidis. Therefore, only choice D, Chocolate agar, supports the growth of N. meningitidis due to its enriched composition.